Replace or repair

G'day JonnyD. Anything is possible but I suspect your first step is to get up there and have a really good look at just how much of the original timber is left. The area in the third picture looks to be the one that needs attention, so dig that one out first. Question: Are these boards actually made of timber? Many homes were fitted with an Asbestos based materials and you will not want to get involved with that at all.

The timber will have to be completely dry before you do anything, sealing a damp timber may trap the moisture and rot the timber to the point it has to be replaced.

When you have some idea of how big your problem is, have a chat with your local hardware outlet about what products are available that can be painted over with the type of filler or sealant you plan to use.

PS. I have the cement based boards and damaged one board with a cricket ball. Sealed it up with some Sikaflex 11FC I had laying around, that was about 12 years ago, I had to look very close to find it, noticed the younger paint first.

Good luck and fair winds.

Have another look at the boards you suspect may need ripping down. Because most boards have an overlap at the top that tucks under the board above to prevent moisture from getting behind the boards, so you might not have to cut them at all. Also, note these boards use galvanised nails to prevent rusting. I hope this helps.

You want to fix the position of the downpipe, facing it towards the house has most likely caused the damage